Plasma arc welding back gas protection device

The utility model discloses a plasma arc welding back gas protection device. The device comprises a base plate, a ventilation pipe and cladding plates. A groove is opened on the upper surface of the base plate, the ventilation pipe is accommodated in the groove of the base plate, the cladding plates are fixed on the upper surface of the base plate, a gap communicated with the groove is left, and uneven gas holes are opened on the ventilation pipe. According to the plasma arc welding back gas protection device, protection gas is transmitted through the ventilation pipe and the opened uneven gas holes, so that under the circumstance that the inertia protection gas flow consumption is reduced relatively, the integral evenness of the protection gas is improved, the gas protection effect on short and long longitudinal seams is well achieved, and the welding quality is improved.